Fusible safety-plug.



J. T. DODSON.

FUSIBLE SAFETY PLUG.

APPLlCATlON FILED SEPT. 28. 1914 1 5 1,76%. Patented Aug. 31, 1915;.

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JOB T. DGDSON, 0F KERKSVILLE, MISSOURI.

FUSIBLE SAFETY-PLUG.

Specification of Letters Patent.

Patented Aug. 31, 1915.,

Application filed September 28; 1914. Serial No. 863.841.

To all 10/1 out it may concern Be ltliIlOWIl that Leon T. Doosox, a citi- Zen of the UnitedStates-and a resident of the city of Kirksville. county of Adair, and State of Missouri. have invented a new and useful Improvement in Fusible Safety- Plugs, of which the following is a. specification.

This invention relates to safety devices for steam boilers and other pressure apparatus which is subjected to external heat, and more particularly to a fusible plug which may be secured in a suitable opening in a wall of the apparatus.

The invention consists in an improved fusible plug having means for making it respond quickly to an excessive temperature. The invention also consists in such a plug having means for causing it to function properly irrespective of the condition of the inside of the wall of the apparatus to which it is applied. i

The plug comprises compressed helical spring which is embedded in the fusible metal, the object'of this arrangement being to provide means for breaking up scale or sediment of any kind which may cover the inner end of the plug. The plug also comprises a heat conducting element extending through the fusible metal for the purpose of causing the metal to melt from end to' end simultaneously in case it is subjected to excessive heat.

Further objects of the invention appear in connection with the following description of the device embodying the invention illus trated in the accompanying drawings.

Referring to the drawings, in which the parts are designated by the same reference characters in the several views, Figure 1 is a side elevation of the device; Fig. 2 is a longitudinal section through the center of the device, showing the heat conducting rod in side elevation; Fig. 3 is a view of the outer end of the device; Fig. 4 is a view of the inner end of the device and Fig. 5 is a side view of the compression spring.

The device consists of a tubular shell-11, having screw threads 12 on its exterior for the greater part of its length, and with one end 13 hexagonal on the outside to provide a convenient means for screwing the shell into a threaded holein a boiler or other pressure containing vessel which is to be subjected to external heat. The bore 1 1 of the shell tapers inwardly from the screw threaded or inner end of the shell to an internal. flange 15 at the hexagonal. or outer end of the. shell.-. An annular groove lb is cut in the bore of the shell near the screw threaded end.

A spiral or helical compression spring 17 is compressed into the bore of the shell with one end of the spring seated against the flange 15 and the other end flush with the inner end of the shell. and a filling 18- of fusible. metal is cast around the spring, filling the bore 14 and groove 16. and firmly embedding the spring therein.- A metal rod 19 having relatively 'high heat conductivity, such as copper or silver. isarranged axially through the bore with its ends terminating flush with the end faces of the fusible metal filling. This rod 19 may be cast in position in the fusible metal, or a hole may be made through the fusible metal after it is cast. and the rod driven into it. The end of the rod at the larger end of the bore is formed with a flaring head 20. and the fusible metal filling is recessed to receive it.

The complete device constitutes a safety plug which is quick acting and positive in its response to any rise in temperature above the melting point of the fusible alloy used for the filling. The center rod conducts the heat to the extreme inner end of the fusible filling and causes it to melt around the rod from end to end. When the metal has melted sufficiently for the head of the rod to pass through the flanged end of the bore the contents of the boiler or other apparatus will blow out and give warning of will not lose its spring temper at the melting temperature of the fusible metal filling.

It is evident that the specific forms and arrangement of the parts may be modified without departing from the invention.

The invention is not restricted to the specific forms and arrangements of the several parts as shown herein, except in so far as is required by the claims.

What I claim as my invention is as follows:

1 A safety plug comprising a shell with open ends, a filling of fusible metal within said shell, and a compressed spring member completely embedded in said filling and held in compressed condition solely by said filling.

' 2. A safety plug comprising a shell with open ends having an internal flange at one end, a fillingxof fusible metal within said shell, and a compressed spring m'ember bearing at one end againstsaid flange and completely embedded in said filling.

3. A- safety plug comprising a tubular shell adapted-to be secured in a boiler and ing of fusible metal within said tubular member, and a solid rod embedded in and extending through said filling in intimate contact therewith from its inner to its-outer face, said rod being made of a metal which is a good conductor of heat whereby the inteapplication of heat to either face.

5 A safety plug comprising a tubular member adapted to b secured in a boi1er, a filling of fusible metal within said tubular member,- a compressed coil spring completely embedded therein, and a rod extending through said filling from its inner to its outer face, said rod being of a metal which is a good conductor of heat.

6. A safety plug comprising a tubular member adapted to be secured in a boiler, the hole through said plug being smaller at the outer end than at the inner, end, a filling of fusible metal within said tubular member, a compressed coil spring embedded therein, an axial hole through said filling, said hole having a counterbore at its inner end, and a rod in'said hole and extending through said filling from its inner to its outer face and havingan enlargement at its inner end seated in said counterbore, sald rod being made of a metal which is argood conductor of heat.

Signed at-Kirksvi'lle, Mlssourl, this 25th day of September, 1914.

JOB T. DODSON.

Witnesses:

J. E. PIEZER, J. E. LANDER. 

